Should I get a dental implant or try post and crown?

If the tooth has broken off at or below the bone level the prognosis for a long lasting restoration is not good.  That does not necessarily mean that you can't have a post, core  and crown made to restore the tooth, however, the chance of failure is going to be high.  An an implant would be a better investment for a long term restoration and less risky. If if you understand that there is a higher risk and decide to go ahead with a post and crown that may be fine for a while but just understand that you could put in a lot of money into this tooth, have it fail, and then still wind up in the same predicament.  I guess you need to decide if the risk is worth trying to keep the tooth rather than a less risky long term restoration. 

Sorry to hear you are having a problem with your tooth.  Implants have the best long term success rates but considering you are 69 years old you may be able to restore with with a post and core.  Just be aware that the tooth will have a guarded prognosis and may be lost in the future. Good luck